The present invention relates to a toolholder and insert arrangement and, more particularly, to a toolholder and insert arrangement wherein an insert is coupled to a toolholder by a shrink fit coupling.
The use of toolholders with replaceable cutting inserts is well known. Examples of tool arrangements in which toolholders with replaceable cutting insert are used include drilling, milling, turning, and grinding operations. Tools such as ball-nose end mills, drills, and grinding wheels can include cutting inserts having shanks made of extremely hard material, such as cemented carbide, while the toolholder is made of a more easily machinable material, such as tool steel. The hard inserts tend to last longer than similar one-piece tools which must be made of a material suitable for machining. Moreover, because the inserts are replaceable, the toolholder will typically be used for extended periods of time without replacement, even though inserts are replaced periodically.
The inserts are typically secured to the toolholder using some form of mechanical connection, such as a screw through the insert, or a set screw or other clamping arrangement. U.S. Pat. No. 4,293,253 and WO 96/06702 disclose toolholders and inserts having a mechanical connection wherein an insert is screwed into a toolholder. A drawback to such conventional toolholder and insert arrangements is that the mechanical connection may fail and damage the toolholder or the insert, or both. Moreover, when a mechanical connection component fails, unless a stock of mechanical connection components is maintained in addition to a stock of toolholders and inserts, the tool must be shut down until a new connection component can be obtained. This can result in undesired expense and loss of productivity. Further still, the mechanical connection components often require specialized tools for connecting the cutting inserts to the toolholders. It is desirable to provide a toolholder and insert arrangement that avoids the need for separate mechanical connection components to secure the insert relative to the toolholder, and that avoids the need for specialized tools for securing the insert relative to the toolholder.
In accordance with an aspect of the present invention, a toolholder and insert arrangement includes an insert having a cutting portion and a shank portion at a base of the cutting portion, and a toolholder having a first end attachable to a spindle and a second end having a shank-receiving opening. When the shank portion is not disposed in the shank receiving opening and the toolholder is at an ordinary room temperature, the shank-receiving opening is smaller than the shank portion, and upon heating of the toolholder to a predetermined temperature above the ordinary room temperature and above an ordinary operating temperature the shank-receiving opening expands to become at least as large as the shank portion and, upon cooling of the toolholder to a temperature below the predetermined temperature and after insertion of the shank portion in the shank-receiving opening, the shank-receiving opening shrinks to generally conform to a shape of the shank portion.